There are two main sections in Zephaniah 1:7–18: Zephaniah 1:7–13 and Zephaniah 1:14–18. Something that helps to identify Zephaniah 1:7 and Zephaniah 1:14 as beginning the two parts of this unit is the repeated focus that each of these verses places on the nearness of the day of the Lord.
A more detailed structure is as follows:
The Day of the Lord (Zephaniah 1:7–18)
The Day of Sacrifice (Zephaniah 1:7–13)
Introductory statement (Zephaniah 1:7)
The Lord’s sacrifice (Zephaniah 1:8–9)
The destruction of city quarters (Zephaniah 1:10–11)
The destruction of Jerusalem (Zephaniah 1:12–13)
The Day of Wrath (Zephaniah 1:14–18)
The day of full rage (Zephaniah 1:14–16)
The day of universal destruction (Zephaniah 1:17–18)1
7 Be silent before the Lord GOD! For the day of the LORD is near; the LORD has prepared a sacrifice and consecrated his guests.